The present invention relates to a control system for an engine, which includes a hydraulically-operated variable valve timing mechanism and a variable oil pump. The hydraulically-operated variable valve timing mechanism has advance-side and retard-side operation chambers for changing a phase angle of a camshaft with respect to a crankshaft by supplying hydraulic pressure, and a locking mechanism which unlocks, by supplying hydraulic pressure, a locking member for fixing the phase angle of the camshaft with respect to the crankshaft. The variable oil pump supplies oil to hydraulically-operated devices including the variable timing mechanism of the engine via a hydraulic-pressure path.
JP2013-104376A discloses a valve timing control system. The control system is provided with a variable valve timing mechanism, an oil pump, and a hydraulic-pressure control valve. The variable valve timing mechanism has advance-side and retard-side operation chambers and a locking mechanism. The advance-side and retard-side operation chambers are formed by a housing for rotating in cooperation with a crankshaft of an engine and a vane body for integrally rotating with a camshaft, and changing the phase angle of the camshaft with respect to the crankshaft by supplying hydraulic pressure. The locking mechanism unlocks, by supplying hydraulic pressure, a locking member for fixing a phase angle of the camshaft with respect to the crankshaft. The oil pump supplies oil to the variable valve timing mechanism. The hydraulic-pressure control valve controls the hydraulic-pressure to be supplied to the locking mechanism and the advance-side and retard-side operation chambers of the variable valve timing mechanism. Further, when changing a phase angle of the variable valve timing mechanism, the hydraulic pressure is calculated before and after being controlled by the hydraulic-pressure control valve, and based on the calculated values, a timing of the hydraulic pressure control by the hydraulic-pressure control valve is retarded. Thus, in the variable valve timing mechanism, unlocking failure of the locking member of the locking mechanism can be reduced.
However, in JP2013-104376A, since the timing of the hydraulic-pressure control by the hydraulic-pressure control valve is retarded when changing the phase angle of the variable valve timing mechanism as described above, there is a disadvantage in that a phase angle control suitable for an operating state of the engine cannot be performed.